This invention relates to a fuel cooling system for a motorvehicle, capable of preventing temperature rise of gasoline or fuel in the fuel tank of the motorvehicle.
The gasoline or fuel supply pipes and the fuel return pipe for the engine of automobiles are heated due to temperature rise of the engine compartment or to radiation heat from the road surface so that the fuel temperature in the pipes is caused to rise, which in turn causes temperature rise of the fuel in the fuel tank. As a consequence, vapor of the fuel is generated in the fuel tank, which vapor is adsorbed by the canister containing activated carbon for preventing leakage of the fuel vapor into the atmosphere.
In recent years the density of parts in the engine compartment has become high and therefore the fuel temperature tends to increase so that where the external temperature is high, a large quantity of fuel vapor is generated to such a degree that the quantity of the generated fuel vapor exceeds the adsorption capacity of the canister. Thus, there arises a dangerous condition of the fuel vapor being discharged to the outside to a greater degree. Furthermore, due to the evaporation of the fuel, a vapor locking phenomenon occurs in the fuel pipes. This phenomenon can be prevented only by decreasing the temperature of the fuel.
To decrease the fuel temperature it has been a practice to cool the fuel in the pipes by low temperature refrigerant flowing through a refrigerant return pipe to the compressor of the refrigeration system for the air conditioning of the motorvehicle. For carrying out this cooling, a heat exchanger is provided between the fuel pipe and the refrigerant return pipe as disclosed in Japanese Patent Appln. Laid-open No. HEI 3-43,653.
The heat exchanger of the prior art described above has a construction wherein a fuel flow tube and a refrigerant flow tube are concentrically disposed and radial heat transfer fins are fixed in these tubes. Those fins are parallel radial fins extending transversely to the flow paths in the tubes so that the flow resistance in the tube is too large to ensure a smooth flow of the fuel and refrigerant while preventing temperature rise of the fuel due to the -temperature rise in the modern engine compartment caused by high density of parts therein and due to the provision of an electronic fuel injection device. Flow resistance to the flow of the refrigerant is especially objectionable.